Field of the Invention
The present invention relates to an image forming system, an image forming apparatus, and a storage medium.
Description of Related Art
In a conventionally used image forming system, a sheet processing apparatus which performs stapling, folding, cutting, etc. on a sheet after image forming is connected to an image forming apparatus which forms an image on a sheet.
In such image forming system including an image forming apparatus and a sheet processing apparatus, the image forming apparatus conveys sheets to follow to the sheet processing apparatus while maintaining an interval with forwarded sheets on which certain processing needs to be performed in the sheet processing apparatus. If the image forming apparatus is able to convey the sheets while maintaining an interval no smaller than the interval notified by the sheet processing apparatus, jamming due to the sheets bumping is not caused. With this, the sheet processing apparatus is able to perform predetermined processing.
For example, Japanese Patent Application Laid-Open Publication No. 2000-177921 discloses in a post-processing apparatus including a binding unit, there is a technique to control the interval between the last sheet of a previous bundle and the first sheet of the next bundle considering conveying time of the binding unit which changes according to the interval between the binding positions.
Japanese Patent Application Laid-Open Publication No. 2005-323059 discloses when the post-processing mode is switched, there is a technique to control the interval between the last sheet before changing and the first sheet after changing based on the switching time set in advance for each combination of the post-processing mode before changing and the post-processing mode after changing.
Among the processing performed by the sheet processing apparatus there is processing that needs preparation operation before starting the processing. In the sheet processing apparatus, the necessary preparation operation is performed as fast as possible so that the sheet processing apparatus is promptly in a state to be able to receive sheets from the image forming apparatus. With this, jamming is prevented.
For example, in the sheet processing apparatus, in order to measure the color using a colorimeter, preparation operation such as “white calibration” and “pre-luminescence”needs to be performed. The “white calibration” is processing to read the white surface for calibration (calibration surface) with the colorimeter to determine a reference value of the colorimeter. The “pre-luminescence” is processing in which the LED (Light Emitting Diode) used as the light source in the colorimeter is lit for a predetermined amount of time to stabilize the amount of light.
However, when the colorimeter is used, since the amount of light decreases due to the heat of the LED, the color needs to be measured within a certain amount of time after the preparation operation is completed in order to properly measure the color. When a certain amount of time passes, the preparation operation needs to be done again.
When the color is measured using the colorimeter and the image is formed while maintaining the quality of the shade in the image forming system including the image forming apparatus and the sheet processing apparatus, if the “white calibration” and the “pre-luminescence” as the preparation operation is performed as fast as possible, the color cannot be measured until the first sheet is conveyed to the position of the colorimeter. Therefore, the number of sheets with which the color can actually be measured decreases and productivity decreases.
FIG. 12 shows a state of a colorimeter and a state of the conveyed sheet in each position when the color is measured in the conventional image forming system. The number in each position shows the number of the sheet counted from the first sheet. The horizontal axis shows the time. Here, after the preparation operation (white calibration and pre-luminescence) is completed, the color can be measured for 37 seconds.
In such system, in order to convey the sheet from the sheet feeding start position of the image forming apparatus to the resist position, through the sheet ejecting position and then to the position of the colorimeter, 16 seconds is necessary. Since the preparation operation (white calibration and pre-luminescence) consumes 6 seconds, the color can be measured 6 seconds after the first sheet is fed, but even after the color can be measured the color is not measured for 10 seconds. This results in bad productivity.
In this case, after measuring the color of the 14th sheet which is when the certain amount of time in which the color can be measured ends, the preparation needs to be performed again, and the 15th sheet needs to wait in the image forming apparatus for the amount of time necessary to complete the preparation.